Active cation-integration high-entropy Prussian blue analogues cathodes for efficient Zn storage

Mn-based Prussian blue analogues (Mn-PBAs), featuring a three-dimensional (3D) metal-organic framework and multiple redox couples, have gained wide interests in Zn-ion batteries (ZIBs). However, owing to the Jahn-Teller distortion and disproportionation reaction of Mn3+, these materials suffer from poor electrochemical performances and inferior structural stability. Herein, we prepare a typical high-entropy Prussian blue analogue (HE-PBA) with increased configuration entropy through integrating five transition metal elements of Mn, Co, Ni, Fe and Cu into the nitrogen-coordinated -M- lattice sites. Consequently, the HE-PBA presents enhanced uptake of Zn2+ with 80 mAh·g−1 compared to those medium-entropy PBAs, low-entropy PBAs and conventional PBAs, which can be assigned to "cocktail" effect of multiple transition metal active redox couples. Furthermore, a phase transition process from monoclinic phase to rhombohedral phase occurs in HE-PBA cathode, resulting in a stable structure of MN6 (M = Mn, Co, Fe, Ni, Cu) and ZnN4 co-linked to FeC6 through the cyanide ligands. Additionally, the advantages of entropy-driven stability are also confirmed by the calculated reduction energy and the density of states between HE-PBA and KMn[Fe(CN)6] (KMnHCF). This work not only presents a high-performance HE-PBA cathode in ZIBs, but also introduces a novel concept of high entropy benefiting for designing advanced materials.